The present invention relates generally to well-logs, and more particularly to the presentation of well-logs for deviated well-bores.
In order to make the most effective use of a well-log for interpretation, geo-steering, or similar purposes, a driller, geologist, petrophysicist, or other professional must be able to correlate the measurements displayed on the well-log to geological features through which the well-bore is drilled. Historically, many wells have been drilled vertically; consequently, well-logs are often presented along a single, fixed vertical axis with measurements from the shallower portion of the well being shown at the top of the well-log and measurements from the deeper portions of the well being shown at the bottom. Well-logs presented along a fixed vertical axis allow the person viewing the log to easily correlate well-bore measurements to geological features in vertical wells.
However, many modem wells deviate significantly from the vertical. Non-vertical well bores complicate well-log interpretation, because the readings of many well-logging tools are affected by the angle of inclination. Because some tool measurements differ between a vertical well and a deviated well, it is important to know how much the well-bore deviates from the vertical if one is to properly interpret the well-log. Since vertical logs generally do not provide easy to interpret visual clues concerning the inclination/deviation of a well-bore, traditional well log presentations may not be ideal for assisting someone in properly interpreting a well-log from a deviated well.
An extreme example of a well deviating from the vertical is found in horizontal wells. In horizontal wells, the well-bore may be drilled vertically until a desired depth is reached, after which time the well is purposely deviated to achieve a near horizontal direction. In order to assist users in visualizing the well-bore, the well-log has sometimes been presented along a single, fixed horizontal axis, in much the same way that the well-log for a vertical well is presented along a single, fixed vertical axis.
Since most conventional well-logs are presented along either a horizontal axis or a vertical axis that is chosen and fixed for the entire well-bore, neither a geologist interpreting the well-log nor the driller attempting to properly steer the drill-bit has an easily interpreted aid to assist him in visualizing deviations of the well-bore from the chosen vertical or horizontal presentation axis. Because this lack of visual aid can make it unnecessarily difficult to interpret a well-log of a deviated well, it would be desirable to have available alternative well-log presentation formats.